In recent years, research and development have been carried out on organic EL display panels in which organic EL elements are mounted on a substrate. These organic EL display panels are used as display devices. As an organic EL display panel uses organic EL elements that each emit light, the light from the organic EL display panel is highly visible. Furthermore, each organic EL element is a complete solid state device and thus has excellent impact resistance. Due to the above features, organic EL display panels are starting to spread as displays for small electronic devices (e.g., mobile phones) and televisions in recent years.
An organic EL element is a current-driven light-emitting element, and is normally configured by layering an organic light-emitting layer, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, and the like between a pair of electrodes, i.e., an anode and a cathode. Here, the organic light-emitting layer brings about the phenomenon of electroluminescence due to recombination of carriers.
FIG. 12 is a partial cross-sectional view showing the structure of a conventional organic EL display panel 500. The upper side of the organic EL display panel 500 in FIG. 12 is a display screen. In other words, the organic EL display panel 500 is of a top-emission type. FIG. 13 schematically shows the shape of a bank 57 as viewed perpendicular to the display screen of the organic EL display panel 500. For convenience, organic light-emitting layers 58 and an upper electrode 59 are omitted from FIG. 13. Note that the partial cross-sectional view of FIG. 12 is taken along C-C′ in FIG. 13.
As shown in FIG. 12, a TFT layer 52, power supply electrodes 53, a planarizing film 54, and lower electrodes (anodes) 56 are layered in the stated order on a substrate 51. The planarizing film 54 has contact holes 55 via which the TFT layer 52 and the lower electrodes 56 are brought into conduction. A bank 57 is formed above the lower electrodes 56. The bank 57 is a grid defining openings 60 in which the organic light-emitting layers are to be formed in one-to-one correspondence. Once the organic light-emitting layers 58 are formed in the openings 60 in one-to-one correspondence, the upper electrode (cathode) 59 is layered so as to cover the organic light-emitting layers 58.
As shown in FIG. 13, each opening 60 has a substantially rectangular shape whose lengthwise direction extends along a column (Y) direction. The plurality of openings 60 are arranged in a matrix. Each contact hole 55 is located between a corresponding pair of openings 60 adjacent in the column direction. The contact holes 55 are covered by the bank 57. If the contact holes 55 are not covered by the bank 57, the organic light-emitting layers 58 would not be flat because of the presence of the contact holes 55; this could cause unevenness in light emission and the like. To prevent this problem, the bank 57 is formed so as to cover the contact holes 55 as shown in FIGS. 12 and 13.